The present invention relates to a vehicle drive as recited in the independent claims.
A vehicle having a parallel hybrid drive is known from German Patent Document DE 10 2007 037 758 A1. A crankshaft of the internal-combustion engine is connected with the rotor of an electric machine by way of a torsional vibration damper and a clutch. The rotor of the electric machine is, in turn, coupled with an input shaft of a transmission. Although the internal-combustion engine could be started by the electric machine, a separate starter device is provided for starting the internal-combustion engine. The starter device may be a starter which is coupled with the crankshaft of the internal-combustion engine by means of a belt drive, or which may be a pinion starter. A starting of the internal-combustion engine by way of the electric machine is specifically not provided in German Patent Document 10 2007 037 758 A1 because, as indicated in German Patent Document DE 10 2007 037 758 A1, this would require very high control-related expenditures.
German Patent Document DE 10 2007 061 895 A1 also describes a hybrid drive, in the case of which, for starting the internal-combustion engine, a separate “electric motor” is provided which is coupled with the crankshaft of the internal-combustion engine by way of a belt drive. German Patent Document DE 10 2008 027 658 A1 as well as Japanese Patent Document JP 2001336466 A describe a further hybrid drive of this type.
Modern vehicles are increasingly equipped with a so-called “engine start-stop system.” This is a complicated electronic control, which “automatically” switches off the internal-combustion engine under certain conditions as a function of a plurality of parameters and “automatically” restarts the internal-combustion engine in the presence of certain other conditions. An engine start-stop system will switch off the internal-combustion engine, for example, in stop-and-go traffic, when the vehicle is stopped temporarily. As soon as the driver gives a “start signal,” for example by stepping on the clutch in the case of a vehicle equipped with a manual transmission, the automatic engine start-stop system will restart the internal-combustion engine. In the case of vehicles that are equipped with an automatic engine start-stop system, the internal-combustion engine is therefore switched off and restarted significantly more frequently than in the case of conventional vehicles. During the start of an internal-combustion engine at the operating temperature, in the engine start-stop operation, a starting system has to meet very different requirements than, for example, during a cold start of the internal-combustion engine at a very low temperature level (winter).
It is an object of the invention to create a vehicle drive that has a starting device for starting the internal-combustion engine, which starting device is optimally adapted to the requirements existing under different conditions.
This object is achieved by the characteristics of the independent claims. Advantageous embodiments and further developments of the invention are contained in the subclaims.
The starting point of the invention is a vehicle drive having an internal-combustion engine and a first starting system (first starting device) provided for starting the internal-combustion engine.
According to the invention, for starting the internal-combustion engine, in addition to a first starting system, a second starting system (second starting device) may be provided which can be controlled independently of the latter and operates independently of the latter, neither the first nor the second starting system being provided for generating vehicle propulsion. Vehicle propulsion may be generated (a) exclusively by the internal-combustion engine if the vehicle is a conventional vehicle (non-hybrid vehicle), or (b) by the internal-combustion engine and/or by an electric driving machine if the vehicle is a hybrid vehicle.
However, it may be provided that one of the starting systems or both starting systems is/are used under certain conditions for recuperating mechanical energy and generating electric energy, which can then be stored in a battery system.
The two starting systems may be designed for different starting conditions. For example, one starting system may be designed for cold or low-temperature starts of the internal-combustion engine. If the vehicle is equipped with an engine start-stop system, the second starting system can be used for starting the internal-combustion engine (which is at the operating temperature), after a brief engine stop controlled by the engine start-stop system.
Up to a certain degree, the two starting systems may also have a redundant design. This means that, in the event of a failure of one of the two starting systems, the other starting system can take over the concerned function at least until a repair shop has been reached.
The invention is suitable for conventional vehicles that are equipped exclusively with an internal-combustion engine as the driving engine. As an alternative, the invention can also be used in the case of hybrid vehicles, particularly in the case of vehicles having a parallel hybrid drive, where, in addition to the internal-combustion engine, an electric machine is provided which generates propulsion, whereby the vehicle can optionally be driven only by the internal-combustion engine, only by the electric motor and/or in a combined manner, i.e., by the internal-combustion engine and the electric motor.
One of the two starting systems may, for example, be a pinion starter. Pinion starters are suitable particularly for cold starts of the internal-combustion engine. The other starting system may, for example, be a starter generator which is coupled by means of a belt drive with the crankshaft of the internal-combustion engine and is suitable primarily for starting the internal-combustion engine in the engine start-stop operation, i.e. for a starting after an only temporary switching-off of the internal-combustion engine by an engine start-stop system. If the vehicle is a full hybrid vehicle, which can also be driven purely electrically, the second starting system (for example, the starter generator in the belt drive) can also be used for the additional starting of the internal-combustion engine during purely electric driving.
In the case of a hybrid vehicle (e.g., a vehicle where, in addition to the internal-combustion engine, an electric machine that generates a vehicle propulsion), the electric machine can in principle also be used as a “third starting system” for starting the internal-combustion engine (for example, when the two starting systems have failed).
Which of the two or three starting systems provided in the vehicle is specifically optimal in a certain driving or vehicle state for starting the internal-combustion engine is determined by means of a starting system selection strategy (additional-start manager) implemented in an electronic system of the vehicle. This “additional-start manager” selects the momentarily best suitable starting system and coordinates the individual starting systems.
If a defect is detected in one of the existing starting systems, it may be provided that the automatic engine start-stop system or the additional-start manager will no longer take into account the defective starting system in the further operation and, for starting the internal-combustion engine, will use the remaining starting system or the two remaining starting systems, whereby it is ensured that the driver can continue to drive in an “emergency operating mode”.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.